If they’re organized you can do library imports, after setting up the arrs for the most part. For example your movies folder would need to have a folder per movie named like ‘Movie Title (year)’ at a minimum and then contain the movie…just make sure what you’re seeding in qbit is not the same folder, but you can use hardlinks to keep seeding how qbit wants it while allowing the arrs to keep its copy nice and clean.

I’m pretty sure you can do a library import after you setup the arrs and use them for a while, you just need to utilize categories is qbit so the arrs only look at their specific category.

Read through their wiki getting started and faq and check out the trash guides.